Imaging device, electronic device, and light detecting method

Abstract

[Problem] To provide an imaging device that can detect a rapid luminance change.[Solution] An imaging device according to an embodiment of the present disclosure includes: a photoelectric conversion circuit that generates a pixel signal corresponding to a luminance of incident light; and a reading circuit that reads the pixel signal from the photoelectric conversion circuit. The reading circuit includes: a first amplifier circuit that reads the pixel signal in a first period; a second amplifier circuit that reads the pixel signal in a second period subsequent to the first period; an adding circuit that adds a first output signal of the first amplifier circuit and a second output signal of the second amplifier circuit; and a comparator circuit that detects a change of the luminance on the basis of a third output signal of the adding circuit.

1 . An imaging device comprising: a photoelectric conversion circuit that generates a pixel signal corresponding to a luminance of incident light; and
 a reading circuit that reads the pixel signal from the photoelectric conversion circuit,   wherein the reading circuit includes:   a first amplifier circuit that reads the pixel signal in a first period;   a second amplifier circuit that reads the pixel signal in a second period subsequent to the first period;   an adding circuit that adds a first output signal of the first amplifier circuit and a second output signal of the second amplifier circuit; and   a comparator circuit that detects a change of the luminance on a basis of a third output signal of the adding circuit.   
     
     
         2 . The imaging device according to  claim 1 , wherein the reading circuit is disposed between the second amplifier circuit and the adding circuit and further includes a sampling hold circuit that temporarily holds the second output signal. 
     
     
         3 . The imaging device according to  claim 2 , wherein the second amplifier circuit has a circuit configuration identical to a circuit configuration of the first amplifier circuit. 
     
     
         4 . The imaging device according to  claim 3 , wherein the first amplifier circuit includes a first P-type transistor, a first N-type transistor connected in series with the first P-type transistor, and a first switch disposed between a gate of the first P-type transistor and a source of the first P-type transistor,
 the second amplifier circuit includes a second P-type transistor, a second N-type transistor connected in series with the second P-type transistor, and a second switch disposed between a gate of the second P-type transistor and a source of the second P-type transistor,   in the first period, the first switch is placed in an off-state and the second switch is placed in an on-state, and   in the second period, the first switch is placed in an on-state and the second switch is placed in an off-state.   
     
     
         5 . The imaging device according to  claim 4 , wherein the sampling hold circuit includes a third switch disposed between the second amplifier circuit and the adding circuit, and a capacitor with one end connected to the third switch and the adding circuit and the grounded other end, and
 the third switch is placed in an off-state in the first period and is placed in an on-state in the second period.   
     
     
         6 . The imaging device according to  claim 1 , further comprising a pixel array part including a plurality of pixels arranged in a two-dimensional array,
 wherein each of the plurality of pixels includes the photoelectric conversion circuit and the reading circuit.   
     
     
         7 . The imaging device according to  claim 5 , wherein the imaging device is configured with a P-type transistor or an N-type transistor that is driven on a basis of a reset signal with a signal level changing at timing of switching of the first switch, the second switch, and the third switch from the first period to the second period. 
     
     
         8 . The imaging device according to  claim 7 , wherein the first switch, the second switch, and the third switch are each configured with a third P-type transistor, and
 the imaging device further includes an inverter that inverts the signal level of the reset signal inputted to the second switch.   
     
     
         9 . The imaging device according to  claim 7 , wherein the first switch and the third switch are each configured with a third P-type transistor, and
 the second switch is configured with a third N-type transistor.   
     
     
         10 . The imaging device according to  claim 5 , wherein the sampling hold circuit includes a third switch disposed between the second amplifier circuit and the adding circuit, and a capacitor with one end connected to the third switch and the adding circuit and the grounded other end, and
 the third switch is placed in an on-state in the first period and the second period.   
     
     
         11 . The imaging device according to  claim 7 , further comprising a pixel logic circuit that drives the photoelectric conversion circuit and the reading circuit. 
     
     
         12 . The imaging device according to  claim 11 , wherein the pixel logic circuit generates the reset signal. 
     
     
         13 . The imaging device according to according to  claim 1 , wherein the second period is a reset period of the first amplifier circuit, and a length of the reset period is fixed. 
     
     
         14 . The imaging device according to  claim 10 , wherein the second period has a length that is variable according to the detection result of the comparator circuit. 
     
     
         15 . The imaging device according to  claim 1 , wherein the comparator circuit includes:
 a first comparator that outputs a result of a comparison of the third output signal with a predetermined upper limit threshold value; and   a second comparator that outputs a result of a comparison of the third output signal with a predetermined lower-limit threshold value.   
     
     
         16 . An electronic device comprising an imaging device including: a photoelectric conversion circuit that generates a pixel signal corresponding to a luminance of incident light; a first amplifier circuit that reads the pixel signal in a first period; a second amplifier circuit that reads the pixel signal in a second period subsequent to the first period; an adding circuit that adds a first output signal of the first amplifier circuit and a second output signal of the second amplifier circuit; and a comparator circuit that detects a change of the luminance on a basis of a third output signal of the adding circuit. 
     
     
         17 . A light detecting method comprising: generating a pixel signal corresponding to a luminance of incident light;
 reading the pixel signal in a first period by a first amplifier circuit;   reading the pixel signal in a second period subsequent to the first period by a second amplifier circuit different from the first amplifier circuit;   adding a first output signal of the first amplifier circuit and a second output signal of the second amplifier circuit by an adding circuit; and   detecting a change of the luminance on a basis of a third output signal of the adding circuit.